This invention relates to an elevator control apparatus capable of an earthquake mode operation, and more particularly to the automatic reset control thereof.
In an elevator, safety is secured at the occurrence of an earthquake by switching an ordinary operation to an earthquake mode operation.
FIG. 3 is a block diagram showing an example of the elevator which performs a conventional earthquake mode operation as disclosed in Japanese Patent Application Publication No. 54-9375 (corresponding to U.S. Pat. No. 3,792,759). Referring to the figure, numeral 1 designates a first control device which controls the service of the elevator, and numeral 2 a second control device which controls the earthquake mode operation through the first control device 1 when an earthquake has occurred. The second control device 2 has an acceleration detector 3 which detects the acceleration of vibrations applied to the elevator due to the occurrence of an earthquake. A first level detecting circuit 4 generates a first level detection signal P.sub.1 and supplies it to the first control device 1 when an output signal from the acceleration detector 3 has exceeded a first set level L.sub.1.
A second level detecting circuit 5 generates a second level detection signal P.sub.2 when, after exceeding the first set level L.sub.1, the output signal supplied from the acceleration detector 3 has had its amplitude decreased below a second set level L.sub.2 which is lower than the first set level L.sub.1. A timer circuit 6 begins timekeeping in response to the second level detection signal P.sub.2, and generates a time lapse signal Q and supplies it to the first control device 1 when a predetermined period of time T.sub.1 has lapsed. The acceleration detector 3 is fixed at the uppermost floor which is affected most intensely by the earthquake.
The control circuit arranged as described above operates as will now be explained. When an earthquake has occurred, vibrations on the ground become as shown in (a) of FIG. 4 by way of example. In response to these vibrations, the output signal of the acceleration detector 3 becomes as shown in (b) of FIG. 4, the vibrations being largest in the uppermost floors part of a building. Here, when the output signal of the acceleration detector 3 has risen above the first set level L.sub.1 indicated in (b) of FIG. 4, the first level detecting circuit 4 detects this state and generates the first level detection signal P.sub.1 at a point of time t.sub.1 indicated in (b) of FIG. 4. In this case, the first set level L.sub.1 is a level by which the ordinary operation of the elevator might be affected and which is preset in consideration of the individual character etc. of the building. Therefore, the generation of the first level detection signal P.sub.1 indicates that the vibrations ascribable to the earthquake have approached the level which exerts influence on the ordinary running of the elevator. Accordingly, when supplied with the first level detection signal P.sub.1, the first control device 1 stops the running of the cage of the elevator at the nearest floor by virtue of a normal stopping operation so as to secure safety.
Subsequently, when the vibrations attributed to the earthquake have gradually decreased until the maximum amplitude level has consequently lowered below the second set level L.sub.2, the second level detector 5 is actuated to generate the second level detection signal P.sub.2 at a point of time t.sub.2. In this case, the second set level L.sub.2 is a level at which the influence on the ordinary running of the elevator lessens and which is preset in consideration of the individual character etc. of the building. Accordingly, the generation of the second level detection signal P.sub.2 signifies that the state in in which the running of the elevator is possible has been approached owing to the weakened earthquake vibrations of the building.
When the second level detection signal P.sub.2 has been generated, the timer circuit 6 is triggered thereby to start its timekeeping operation. When the predetermined period of time T.sub.1 has lapsed, the time lapse signal Q is generated and is fed to the first control device 1. Here, the period of time T.sub.1 is set at a time interval from the point of time t.sub.2 at which the amplitude of the output signal generated by the acceleration detector 3 decreases below the second set level L.sub.2, till a point of time t.sub.3 at which the output signal of the acceleration detector 3 becomes sufficiently small. Thus, when supplied with the time lapse signal Q, the first control device 1 executes the processing of automatically resetting the elevator in the stop state and restoring it to the ordinary operation.
However, the elevator control apparatus including the control circuit for the earthquake mode operation based on the above arrangement has a problem. The elevator in the stop state is automatically reset at the point of time t.sub.3 at which the predetermined time interval T.sub.1 has lapsed since the point of time t.sub.2 at which the amplitude of the output signal delivered from the acceleration detector 3 had decreased below the second set level L.sub.2. In this regard, the delay in time of the output signal of the acceleration detector 3 differs greatly depending upon the direction of occurrence and the scale of occurrence of the earthquake and the individual character of the building. Therefore, the time of the automatic reset (the fixed period of time T.sub.1) does not always become proper.